smelly water butt - no jokes please!

[SoTiredOfTheWheelsOnTheBus]

yes, I know this sounds like something out of an extremely dodgy 'comedy', but please, try to keep the jokes to a minimum .

We installed a water butt in the garden a couple of months ago, but have now noticed that when we decant water out of it, it smells bad. It's a kind of sewagey/sulphurish smell, quite unpleasant. The water butt has a well-fitting lid, so I don't think there can be anything dead/decaying in there.

I didn't know if it could be leaves from the gutters being washed into the pipe, but it's not really the right time of year for that.

Is this a common problem, or do we just have smelly rain where we live?

I had this problem as a one off recently, and came to the conclusion that it was due to the water getting stagnant over winter. It went after that round of water was used up, and hasn't returned. Didn't seem to do the plants any harm.

Hi my DH is a gardener and says it won't do the plants any harm at all. The smell will be from some kind of plant matter (leaves most probably) decaying in there.
If it's really stinky you could empty it completely and put a filter somewhere in the downpipe?
Hope that helps ...

hilarious title. pmsl